Once eggs and sperm have been collected, the actual process of injecting a single sperm into the egg is carried out in a laboratory. The injection is performed on a heating stage, on a specialized inverted microscope (which allows one to magnify details up to 400 times) equipped with Hoffman modulation contrast optics (which enhance "optical contrast", so that the details of the egg can be visualized easily). The precise control that is needed for microinjection is provided by using specialized micromanipulators, which allow one to execute very fine movements.
The eggs and sperm are manipulated using fine glass pipettes, made of thin capillary tubing, which are even finer than a human hair. These are custom made, the holding pipette being designed to hold a single sperm. Live sperm are placed in a drop of viscous polyvinyl pyrrolidone (PVP) solution, which serves to slow down the activity of the sperm. (It is helpful to slow down the sperm, so that they can be picked up more easily by the injecting needle.) A single sperm is then selected and its tail is pinched or broken to immobilize it. This is usually done by crushing the sperm tail by rolling it between the injection pipette and the base of the petri dish. It is essential to immobilize the sperm, so that it cannot move after it has been injected into the egg. A single immobile sperm is then picked up by sucking it into the injection pipette.
The egg is secured in place by applying gentle suction to its shell (the zona) with a holding pipette. The sperm is then injected directly into the centre (cytoplasm) of the egg by moving the injection pipette very precisely with the help by moving the injection pipette very precisely with the help of the micromanipulator into the egg, and then blowin